1. Field of the Invention
The present invention relates to a fixing device and an image forming apparatus.
2. Description of the Background
In a typical fixing device, a pressing roller is pressed against a fixing roller comprising a soft elastic body, whose surface is covered with a fluorine-containing resin. As a paper sheet passes through a pressing point between the pressing roller and the fixing roller, an edge of the sheet strongly scratches the fixing roller due to a linear velocity difference generated between a portion where the fixing roller contacts the edge of the sheet and a portion where the fixing roller contacts the pressing roller.
Thus, as small-size sheets (e.g., postcards) continuously pass the pressing point, both edges of the small-size sheets in width direction make scratches on the fixing roller. The scratches undesirably appear as low-gloss lines in a solid image formed on a large-size sheet (e.g., A4 sheet) thereafter.
In a market in which the maximum-size sheet in use is A4 or LT and small-size sheets are not frequently used, the above-described problem may not frequently occur. By contrast, in a market in which the maximum-size sheet in use is greater than A4 or LT and A4 or LT sheets are frequently used, the above-described problem frequently occurs.
In view of this situation, there has been a proposal to even out the scratches with a cleaning member or another proposal to remove paper powders that accelerate scratch making, in Japanese Patent Application Publication Nos. (hereinafter “JP-A”) 2003-21980, 2007-3985, 2005-208422, and 2006-251165, for example.
However, the cleaning members disclosed in JP-2003-21980-A and JP-2007-3985-A have smooth surfaces that cannot effectively remove paper powder within a short time period. Even if the surface is rough, toner may be fixedly adhered to the cleaning member and adversely scratch the fixing roller. A technology disclosed in JP-2005-208422-A does detect scratch but does not prevent scratch. A technology disclosed in JP-2006-251165-A does not prevent scratch either.